How to Splice Copper to Aluminum Wire

Standard connectors like these won't work for copper-to-aluminum connections.
Standard connectors like these won't work for copper-to-aluminum connections. (Image: wire nuts image by Paul Moore from Fotolia.com)

You may find it necessary to connect, or splice, an aluminum wire to a copper wire when installing a new circuit or replacing an electric furnace. Take special care when making this type of splice, as an improper copper-to aluminum-splice can become unstable over time, according to certified electrician Glen Baxter. An improper splice can corrode and overheat, eventually creating enough heat to cause a fire. Check your wires carefully before making a splice. You will mostly find aluminum wiring in older homes, but some electricians still connect aluminum wiring to electric furnaces, Baxter says.

Things You'll Need

  • Wire stripping tool
  • Splice-bolt connector with copper alloy spacer for aluminum-to-copper connection
  • Splicing tape
  • Two adjustable wrenches

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Strip about 1/2 inch of the wire insulation off the wires you plan to splice together using your wire stripping tool.

Insert the copper and aluminum wires into the splice-bolt connector opening. Check the placement of the wires to ensure that the alloy spacer separates the stripped section of the wires. Also, check the connection between the wires and the splice-bolt to ensure that the connection area is free of wire insulation. Strip the insulation further if it makes contact with the splice-bolt.

Tighten the nut on the splice-bolt until you have secured the wires. Use two wrenches—one for the bolt head and one for the nut. Take care to ensure an extremely tight connection; aluminum expands and contracts more than copper and can loosen the connection over time if you do not tighten it sufficiently.

Test your connection by pulling on the wires; they should not budge. Retighten if necessary.

Wrap the connection with splicing tape until you have covered all exposed metal with two layers of tape. Overlap the tape as you wrap the connection.

Tips & Warnings

  • Only licensed electricians should perform this type of splice, as an incorrect connection can result in fire.

References

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